Transducer carrier for disk file with liquid film head-disk interface

ABSTRACT

A disk file with substantially reduced head-disk spacing and corresponding improvement in recording performance uses a disk coated with a film of conventional high viscosity lubricant, a lubricant reservoir for replenishing the lubricant on the disk over the life of the file, and a transducer carrier with feet which ski on the high viscosity liquid film. The file does not include any means for recirculating the lubricant since the lubricant spins off the disk at a relatively low rate due to its high viscosity. The lubricant reservoir contains a very small amount of lubricant and thus may be maintained inside the substantially sealed disk file. In one embodiment of the invention, the sealed disk file is essentially evacuated. The operation of the disk file in a near vacuum environment is possible because, unlike conventional disk files, air is not required to support an air-bearing head-disk interface and the high vapor pressure of the relatively high molecular weight lubricant prevents its evaporation.

TECHNICAL FIELD

This invention relates to data recording disk files. More particularly,the invention is a new type of disk file wherein the head or transducercarrier and a liquid lubricant on the disk surface provide a new type ofhead-disk interface.

This application and a co-pending concurrently filed application Ser.No. 07/724,646, are based on a common specification. This applicationclaims the transducer assembly and application Ser. No. 07/724,646claims the disk file.

BACKGROUND OF THE INVENTION

Disk files, also referred to as disk drives are information storagedevices which utilize a rotatable disk with concentric data trackscontaining the information, a head or transducer for reading or writingdata onto the various tracks, and an actuator connected to a carrier forthe head for moving the head to the desired track and maintaining itover the track centerline during read or write operations. There aretypically a plurality of disks separated by spacer rings and stacked ona hub which is rotated by a disk drive motor. A housing supports thedrive motor and head actuator and surrounds the head and disk to providea substantially sealed environment for the head-disk interface. Inconventional magnetic recording disk files the head carrier is anair-bearing slider which rides on a bearing of air above the disksurface. The slider is urged against the disk surface by a small forcefrom a suspension which connects the slider to the actuator, so that theslider is in contact with the disk surface during start and stopoperations when there is insufficient disk rotational speed to maintainthe air bearing. A lubricant is required on the disk surface to preventdamage to the head and disk during starting and stopping of the diskfile.

The conventional magnetic recording disk file suffers from severaldisadvantages which are due to the air-bearing head-disk interface. Thespacing between the head and disk is limited by the minimum achievableflying height of the air bearing slider, which means the recordingperformance of the disk file, which is directly related to this spacing,is accordingly limited. When the slider has been in stationary contactwith the disk for a relatively short period of time, the liquidlubricant and the relatively large air-bearing surface of the slidercreate static friction (or "stiction") forces which cause the slider tostick to the disk surface, which can result in damage to the head, diskor suspension when the slider breaks free from the disk at start up ofthe disk file. The interface, which is primarily a thin film of air whenthe disk file is operating, provides very little stiffness between thehead and disk so that the disk file is very sensitive to vibration andimpact, which makes the conventional disk file undesirable for certainapplications, such as use in a portable computer. The air requiredinside the disk file to support the air-bearing slider also increasesthe air drag on the rotating disks, thereby increasing the powerconsumption, contributes to the noise level in the outside environment,causes buffeting of the suspension, and increases the corrosion andoxidation of the heads, disks and electronic components.

There are several references which describe different types of headcarriers and liquid bearings as possible alternatives to theconventional air-bearing head-disk interface in magnetic recording diskfiles. In assignee's U.S. Pat. No. 2,969,435, a sled-type transducercarrier with a large flat surface rides on a layer of oil on the disk,the oil being supplied from an oil reservoir external to the disk fileand discharged from a nozzle located ahead of the carrier. In assignee'spending application, U.S. Ser. No. 264,604, filed Oct. 31, 1988, andpublished May 9, 1990 as European published application EP 367510, adisk file utilizes a continuously recirculating low viscosity liquidlubricant, which is maintained as a relatively thick layer on the disk,and a transducer carrier which has triangular shaped feet to plowthrough the low viscosity liquid layer. The EP reference suggests thatif the disk file is hermetically sealed with no air present the lowvapor pressure lubricant can evaporate which allows the requiredrecirculation of the lubricant to occur by distillation.

What is needed is a disk file with a liquid bearing interface whichprovides minimal head-disk spacing and which does not require continuousrecirculation of the lubricant.

SUMMARY OF THE INVENTION

The present invention is a disk file having a disk coated with a film ofconventional high viscosity lubricant, a lubricant reservoir forreplenishing the lubricant on the disk over the life of the file, and atransducer carrier having a surface which enables the carrier to ski onthe surface of the high viscosity liquid film. The file does not includeany means for recirculating the lubricant since the lubricant spins offthe disk at a relatively low rate due to its small film thickness andhigh viscosity. The viscosity of the lubricant is high enough to limitthe lubricant loss over the required lifetime of the disk drive to anamount which can be replenished by the reservoir. The lubricantreservoir contains a very small amount of lubricant and thus may bemaintained inside the disk file housing. In the preferred embodiment ofthe invention the reservoir is a sealed ring located near the diskinside diameter and which has a porous interior for holding thelubricant by capillary action and a number of outlets for releasing thelubricant to the disk during rotation of the disk. The preferred surfaceof the transducer carrier is a plurality of ski feet formed as generallytruncated cones which extend from the carrier, the degree of taper ofthe cones being so gradual as to permit the generally circularly shapedends of the ski feet to ski on the lubricant film surface. The generallycircular shape of the ends of the ski feet improves the operation of thecarrier in rotary actuator disk files in which the direction of motionof the carrier relative to the disk varies with the radial position ofthe carrier on the disk. In one embodiment of the invention, the diskfile is sealed and essentially evacuated. The operation of the disk filein a near vacuum environment is possible because, unlike conventionaldisk files, air is not required to support an air-bearing head-diskinterface and the high vapor pressure of the relatively high molecularweight lubricant prevents its evaporation. Thus, the problems associatedwith the presence of air inside the disk file are substantiallyminimized.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in section of a schematic of the disk drive of thepresent invention;

FIG. 2 is an open top view of the disk drive depicted schematically inFIG. 1;

FIG. 3 is a perspective view of the spacer ring lubricant reservoirshown in partial cutaway;

FIG. 4 is a plan view of the bottom of the disk carrier of the presentinvention;

FIG. 5 is a plan view of the bottom of an air-bearing slider modified tohave the ski surface of the present invention;

FIG. 6 is a side view of an alternative transducer carrier;

FIG. 7 is a sectional view of the carrier disk-interface of the presentinvention;

FIG. 8 is a graph of the stiction forces on the transducer carrier as afunction of disk drive start/stop cycles;

FIG. 9 is a comparison of frequency roll-off curves for a conventionalair-bearing head-disk interface disk drive and the disk drive of thepresent invention; and

FIG. 10 is a graph of carrier-disk spacing for a conventionalair-bearing head-disk interface and the head-disk interface of thepresent invention as a function of time during a vibration test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is illustrated in sectional view aschematic of the disk file of the present invention. The disk filecomprises a base 10 to which are secured a disk drive motor 12 and anactuator 14, and a cover 11. The base 10 and cover 11 provide asubstantially sealed housing for the disk drive. Typically there is agasket 13 located between base 10 and cover 11 and a small breather port(not shown) for equalizing pressure between the interior of the diskfile and the outside environment. This type of disk file is described asbeing substantially sealed since the drive motor 12 is located entirelywithin the housing and there is no external forced air supply forcooling the interior components. A magnetic recording disk 16 is mountedon a hub 18, which is attached for rotation by drive motor 12. Aread/write head or transducer (not shown) is formed on a transducercarrier 20. The carrier 20 is connected to the actuator 14 by means of arigid arm 22 and a suspension 24, the suspension 24 providing a biasingforce which urges the transducer carrier 20 onto the surface of therecording disk 16. During operation of the disk file the drive motor 12rotates the disk 16 at a constant speed, and the actuator 14, which istypically a linear or rotary voice coil motor (VCM), moves thetransducer carrier 20 generally radially across the surface of the disk16 so that the read/write head may access different data tracks on disk16.

FIG. 2 illustrates a top view of the interior of the disk file with thecover 11 removed and illustrates an annular lubricant reservoir 30,which serves as a means for holding a supply of liquid lubricant forreplenishment of lubricant on the surface of disk 16. A thin continuousfilm of a relatively high viscosity lubricant is maintained on thesurface of disk 16 and is replenished by lubricant from the reservoir 30during operation. FIG. 2 also illustrates in better detail thesuspension 24 which provides a force to the carrier 20 to maintain thecarrier into contact with the lubricant film on the disk 16. Thesuspension may be a conventional type of suspension such as that used inmagnetic disk files which have an air-bearing slider. An example is thewell-known Watrous suspension, as described in assignees' U.S. Pat. No.4,167,765, which is incorporated herein by reference. This type ofsuspension also provides a gimballed attachment of the transducercarrier which allows the carrier to pitch and roll as it rides on theliquid lubricant film.

The annular lubricant reservoir 30, which may also serve as a diskspacer in disk files which have multiple disks in a disk stack, is shownin detail in FIG. 3. The reservoir 30 comprises a ring or annulus 32which is machined from a porous, sintered metal, such as sinteredstainless steel. Thereafter the outer surface of the annulus 32 isentirely sealed, either by electroplating a material such as gold or byelectroless plating of a nickel film, to provide a film 34 surroundingthe sintered stainless steel. Openings 36 are then formed in the gold ornickel surface film 34 to unseal the reservoir and provide a means forthe lubricant stored inside to escape. This is accomplished by machiningseveral, e.g. typically 4, small areas on the surface film 34 byetching, ablation or electrostatic discharge machining, which createsthe openings 36 or pores in those areas. The reservoir is then filledwith lubricant by placing it in a vacuum, immersing it in the lubricant,and heating it slightly to increase the rate at which it fills. Thenumber and size of the openings 36 are selected to provide the desiredamount of controlled lubricant escape during operation of the disk file,which is designed to match the rate at which lubricant leaves the disk.When the annulus 32 is designed to also, serve as a spacer ring in diskfiles which have multiple disks supported in a stack on the hub 18, theopenings 36 may be located nearer to the portions of the spacer ringwhich are in contact with the disks, so that selected openings areassociated with one of the corresponding disk surfaces. In addition tothe size of the openings 36, the factors which affect the rate oflubricant leaving the disk include the smoothness of the disk, the diskrotational speed, the viscosity of the lubricant, and the carrierdesign. When the disk is not rotating, the capillary action of theporous sponge-like material of annulus 32 holds the liquid inside thereservoir. While the preferred embodiment of the lubricant reservoir orholding means is the annular reservoir 30 described above andillustrated in FIG. 3, there are numerous alternative reservoirs whichare possible. For example, in some applications where the total runningtime of the disk file is relatively short (e.g. several months), themeans for holding the lubricant may be a non-data band or region on thedisk near the inside diameter of the disk. During the normal disklubrication process, the non-data band of the disk is also lubed, sothat the non-data band contains an additional supply of lubricant forreplenishment of the liquid film. In this embodiment for this specificapplication, it may also be desirable to use a lubricant which has ahigher viscosity so that the rate of depletion is somewhat reduced.

Referring now to FIG. 4, the transducer carrier is illustrated with itsskiing surface depicted as a plurality of ski feet 40, 42, 44 formed ona flat surface 43. The carrier may be formed from the conventionalmaterial used to manufacture air-bearing sliders, such as ferrite or analumina and titanium-carbide ceramic material. The carrier 20 is shownas having a flat, generally planar surface onto which each of the skifeet is formed. The ski foot 44 is near the trailing edge of thecarrier, i.e. the portion of the carrier where the thin film transducer46 or other magnetic recording head is supported on the carrier. Each ofthe ski feet is generally a truncated cone extending from surface 43 andwith a generally circular shaped end which enables the carrier to ski onthe lubricant film, regardless of the direction of movement of thecarrier relative to the disk. In this manner the carrier is capable ofskiing when supported on a rotary actuator which moves the carrier in agenerally arcuate path wherein the direction of motion of the carrierrelative to the disk varies depending upon the radial position of thecarrier.

FIG. 5 illustrates an embodiment of the transducer carrier, denoted 20',wherein the ski feet 40, 42, 44 are formed on a conventional three-railair-bearing slider, such as that described in assignees' U.S. Pat. No.4,894,740. Each of the ski feet 40, 42, 44 is formed on the conventionalbottom surface of the rails 50, 51, 52 by material etching the railsback a few thousand Angstroms, preferably by ion milling oralternatively by reactive ion etching, so that the ski feet are theremaining outer portions projecting outwardly from the rails of theslider. The ion milling is performed in a manner such that there is avery slight taper (approximately less than ten degrees) of the ski feetaway from the outer surface of the rails, which results in the ski feetbeing formed as generally truncated cones. This slight taper of the skifeet allows the transducer carrier to actually ski on top of therelatively high viscosity lubricant film on the disk.

While the preferred embodiment of the skiing surface of the carrier isas depicted in FIGS. 4 and 5, the invention has also been successfullydemonstrated with a skiing surface comprising one or more 1 mm. diametertungsten-carbide ball bearings epoxy bonded to a conventionalair-bearing slider. One embodiment of this type of carrier is shown inFIG. 6. The carrier is a conventional two-rail air-bearing slider 25which has the transducer 46 located on its trailing edge. A single 1 mm.diameter tungsten-carbide ball bearing 26 is epoxy-bonded to the leadingedge of slider 25. The ball bearing 26 serves as a front ski foot andraises the front end of slider 25 to cause the trailing edges of therails, such as edge 27, to serve as rear ski feet.

The interface between the transducer carrier and the disk with thelubricant film is illustrated in FIG. 7. In the preferred embodiment,the disk 16 has as its upper solid portion a conventional amorphouscarbon overcoat film 60, which is typically approximately 250 Angstromsthick. The magnetic layer 62, such as a conventional cobalt alloysputter deposited magnetic film, is located beneath the protectivecarbon overcoat 60. The liquid lubricant is deposited as a film 64,preferably to a thickness in the range of approximately 20 to 100Angstroms, on top of the carbon overcoat 60. A portion of one of the skifeet 40 is depicted as being supported on the lubricant film 64. The endof ski foot 40 has a diameter of approximately 100 microns and istapered at approximately a ten degree angle to an etch depth ofapproximately 4,000 Angstroms. The transducer 46 (FIG. 5) is supportedon the trailing edge of the carrier 20 at the end of ski foot 44, and sois maintained at a spacing of approximately the lubricant film thickness(e.g. 20 to 100 Angstroms) from the top of the recording disk. Duringoperation of the disk file the suspension 24 (FIG. 2) maintains a forceon the carrier 20 forcing the ski feet 40, 42, 44 into contact with thelubricant film 64, which, because it is essentially incompressible,serves as a spacing layer between the carrier 20 and the disk 16. Therelatively small angle between the end of ski foot 40 and the disk (10degrees in FIG. 7) improves the ability of the carrier to ski as itprovides less of a barrier to the lubricant which passes under the endof ski foot 40 during start up of the disk drive.

In the present invention it is possible to improve the overallperformance of the disk file by maintaining a vacuum within the sealedhousing. This can be accomplished by constructing the disk file to havean essentially hermetic seal, for example, in the manner such asdescribed in assignee's U.S. Pat. Nos. 4,367,503 and 4,556,969.

Experimental Results

The invention has been demonstrated experimentally using a commerciallyavailable 2.5 inch rotary actuator disk drive with modification of someof the components.

The disk substrate used was manufactured without any intentional textureand polished as smooth as possible. Both aluminum and glass substrateswere used, although aluminum is the preferred disk substrate. A CoPtCralloy magnetic film was sputter deposited on top of a suitableunderlayer, and a 250 Angstroms thick amorphous hydrogenated carbonovercoat was sputter deposited over the magnetic film. Lubricant wasapplied by dipping the disk in a dilute lubricant-solvent mixture, as iscommon in the industry, except that the lubricant was coated to about100 Angstroms thickness. The exact coating thickness is not critical,however it is desirable to keep the lubricant film as thin as possiblein order to minimize the head-disk spacing. The lubricant can be bondedto the carbon overcoat on the disk by ultraviolet (UV) or thermaltreatment, or a lubricant which self-bonds at room temperature can beapplied. Two classes of lubricants were used, perfluoro-poly ethers(PFPE) and hydrocarbons (HC), both of which are conventional disklubricants. In particular, the PFPE Demnum SP from Daikin self-bonds atroom temperature and can be applied by dipping. The HC lubricant, whichmay be a poly-1-decene type of hydrocarbon such as 174H available fromWilliam F. Nye, Inc., can be bonded using any of the techniques citedabove. Preferably the PFPE lubricants are bonded, but the HC lubricantsare not. The bonded lubricant, if there is any, comprises only afraction of the total lubricant film thickness on the disk. The PFPElubricants have a viscosity in the range of 5 centipoise to 10 poise anda molecular weight preferably greater than approximately 2000 amu. TheHC lubricants have a viscosity in the range of 5 centipoise to 10 poiseand a molecular weight preferably greater than approximately 1000 amu.The lubricant should have a viscosity which, when used with disks havinga specified smoothness and operating at a specified rotational speed, issufficient to both prevent excessive lubricant loss and support theskiing surface of the transducer carrier.

In the experiment, the carrier used was essentially that depicted inFIG. 5 and was made by starting with a slider with a working recordinghead and an existing air-bearing surface. Resist and lithography wereused to define the ski feet on the polished rails 50,51,52 forming theair-bearing surface. The air-bearing surface was then ion-milled away(except where the resist defined the feet) a few thousand Angstroms toproduce the feet. The preferred embodiment includes three feet, two feettoward the front of the air-bearing surface overhanging the taperslightly, and one foot at the rear which includes the recording head.

With this type of carrier and a disk file with an air atmosphere theresult is that the front feet 40, 42 (FIG. 5) ski until full diskrotational speed is attained, and then the front feet "fly". The rearski foot 44 continues to ski at all times. This also reduces the drag.The front ski feet are still required, however, for starting andstopping. The etching or milling depth along with the design of theconventional air-bearing surface are the parameters which can beadjusted to ensure that the front feet fly and that the rear foot skisover the desired range of velocities and suspension preload. Forexample, if the conventional air-bearing slider was designed to fly at5000 Angstroms in the front and 1500 Angstroms in the back, then etchingor milling away 3000 Angstroms of material from the slider rails wouldresult in a carrier which had its rear foot skiing and its front feetflying at approximately 2000 Angstroms. If the carrier were thatdepicted in FIG. 4 all ski feet would ski at all times since there is noair-bearing surface to cause the front ski feet to fly.

A lubricant reservoir such as that described in FIG. 3 was installed inthe disk drive. The reservoir sits pressed up against the disk towardthe disk inside diameter, for example where the disk stack spacers wouldnormally reside. In this manner the reservoir acts as both a lubricantholding means and a disk spacer. The reservoir contained four openings36, each with a diameter of approximately 100 microns. The reservoir wasfilled with approximately 0.2 cc of lubricant. The lubricant used in thereservoir is typically the same as the lubricant placed on the disk.

After the disk and reservoir were installed in the disk drive, thecarrier with a Watrous-type suspension having a 6 gram spring preloadwas installed, and the drive was operated.

The tests conducted on the drive included measurements of stiction,lubricant thickness, drag, wear of the data tracks by opticalobservation, magnetic reading and writing, and vibration resistance.

The stiction measurements, plotted as a function of start/stop cycles inFIG. 8, show a low stiction value, even after 100 thousand start/stopcycles. The stiction force between the carrier and the disk wasmaintained in the range of 3 to 7 grams, which is well below the rangewhere damage can occur to the head or disk at start up of the diskdrive.

Lubricant thickness, as determined by visual observation (by videomicroscope) accompanied by ellipsometry, was measured to be between 20and 100 Angstroms over the surface of the disk. Visual observation alsoconfirmed that the reservoir dispenses lubricant to the disk surface,but only when the disk is spinning, and showed that the lubricant issmoothed by the skiing. The capillary action of the porous metal keepsthe lubricant within the reservoir unless it is overcome by thecentrifugal force of spinning. As the lubricant spreads out onto thedisk, the movement of the carrier during accessing smooths thelubricant. To facilitate this smoothing, the carrier was accessed overall available tracks on the disk periodically, i.e. once every 5minutes. This occasional accessing by the actuator to move the carrierover different radial regions on the disk was sufficient to smooth anyirregularities in the thickness of the lubricant, caused for example byany non-uniform distribution of lubricant from the reservoir. Based onthese experimental results it is estimated that for a single 2.5 inchdisk in a drive operated at a conventional operating speed of 3600 RPMonly approximately 0.01 cc of lubricant would be required to bemaintained in the reservoir for the estimated seven year design life ofthe disk drive. This amount would be sufficient to replenishapproximately 10 Angstroms of the lubricant film per day, assumingcontinuous operation over the seven year design life.

The drag was measured by strain gauges attached to the suspension. Thedrag was determined as a function of the velocity of the disk relativeto the carrier, time, and lubricant thickness. In general the drag wasmaintained below 1 gram at operating velocities.

No wear of the disk was observed by optical measurements made with aresolution of better than 10 Angstroms of material loss.

Magnetic measurements were made to determine the improvement inrecording performance due to the much closer head-disk spacing. Themeasured data showed larger overwrite, higher signal amplitude andbetter frequency roll-off curves than in a conventional air-bearinginterface disk drive using the same head and disk. Referring to FIG. 9,the frequency roll-off curves show the significant improvement of theskiing carrier. The curves in FIG. 9 show that the signal amplitude ishigher in the skiing case and that the response at high frequency fallsoff slower than in the flying case. This implies that higher recordingdensities will be obtained for the skiing case, which is a result of thereduced head-disk spacing.

In an experimental test for the vibration or impact resistance of a diskfile with the transducer carrier, disk, and interface of the presentinvention, the commercially available 2.5 inch disk drive as modifiedwas mounted on a shake apparatus. The transducer carrier was thatdepicted in FIG. 5 and was mounted by a conventional type of suspensionto a rotary actuator. The disk was lubricated with 50 Angstroms of aPFPE type of lubricant, such as Demnum SP, by dipping the disk into thelubricant. The load provided by the suspension to bias the carrier ontothe disk was 5.5 grams and the speed of the disk relative to the carrierwas 7 meters per second. The acceleration test provided by the shakerwas 30 G's forces at 70 cycles sinusoidal. The results of thecarrier-disk spacing was measured by measuring the capacitance betweenthe carrier and the disk and is depicted for this experimental device asline 70 on FIG. 10. The slider-capacitance measurement for the same typeof disk drive, but with the conventional air-bearing interface, isdepicted as line 72 in FIG. 10. The comparison of line 70 and line 72illustrates the significant improvement in head-disk stiffness and diskdrive impact resistance provided by the present invention.

The modified disk drive as described above was also tested in a vacuumenvironment by operating the drive within a vacuum chamber. The pressurewas reduced in the chamber to 10⁻⁶ to 10⁻⁷ Torr. The test resultsobtained were essentially the same as those obtained when the drive wastested in the air environment.

While the preferred embodiments of the present invention have beenillustrated in detail, it should be apparent that modifications andimprovements may be made to the invention without departing from thespirit and scope of the invention as described in the following claims.

What is claimed is:
 1. A transducer assembly for a data recording diskfile of the type wherein a disk has a liquid film on its surface, theassembly comprising:a carrier having an air-bearing surface near itsfront end for supporting the front end of the carrier above the liquidfilm when the disk is rotating at its operational speed and a ski footnear its rear end for skiing on the liquid film when the disk isrotating at its operational speed; and a transducer attached to thecarrier for reading data from or writing data to the disk.
 2. Thetransducer assembly according to claim 1 wherein the ski foot comprisesa generally truncated cone having a generally circularly shaped end. 3.The transducer assembly according to claim 1 wherein the transducer islocated on the carrier near the ski foot.
 4. The transducer assemblyaccording to claim 1 wherein the ski foot is generally sphericallyshaped.
 5. The transducer assembly according to claim 1 furthercomprising means for connecting the carrier to the actuator of the diskfile, the carrier to actuator connecting means including means forbiasing the ski foot of the carrier into contact with the liquid film onthe disk.
 6. The transducer assembly according to claim 5 wherein thecarrier to actuator connecting means includes means for providinggenerally gimballed movement of the carrier, whereby the carrier maypitch and roll as its ski foot is forced into contact with the lubricantfilm during rotation of the disk.
 7. A transducer assembly for a datarecording disk file of the type wherein a disk has a liquid film on itssurface, the assembly comprising:an air-bearing slider having aplurality of rails and a plurality of ski feet extending from the railsfor skiing on the liquid film; and a transducer attached to the sliderfor reading data from or writing data to the disk.
 8. The transducerassembly according to claim 7 wherein each of the ski feet has an endwhich forms an angle relative to the disk surface small enough to permitthe end of the ski foot to ski on the lubricant film on the disk.
 9. Atransducer assembly for a data recording disk file of the type wherein adisk has a liquid film on its surface, the assembly comprising:anair-bearing slider having a plurality of rails and at least one ski footextending from one of the rails for skiing on the liquid film; and atransducer attached to the slider for reading data from or writing datato the disk.